1. Field of the Invention
This invention relates generally to a medical instrument for obtaining access to a site within the body directly inserted through the skin or through an incision in the skin to enable introduction of further medical instruments to the percutaneously accessed site or from the percutaneously accessed site to a more remote site in the body, and more particularly to a combined medical probe and flexible guide wire (or guidewire) for introduction of the further elongated diagnostic or surgical or therapy delivery devices over the guide wire and probe.
2. Description of Related Art
Numerous medical procedures have come into common usage for accessing a site within the body in a minimally invasive manner that avoids surgical exposure of the site to perform a wide variety of diagnostic and therapeutic procedures involving use of a small diameter probe (defined herein as including a needle, a stiff wire, a trocar or the like). Such medical procedures generally involve use of the probe to create a percutaneous (also referred to in the art as transcutaneous or trans-dermal) pathway through the skin and subcutaneous tissue. The probe is either pushed or stuck directly through the patient""s skin or is inserted through a small surgical incision in the skin to a particular percutaneously accessed site of interest or to a starting point of an access pathway to a remote site of interest. Then, the percutaneous pathway is expanded in a variety of ways to enable insertion of larger diameter diagnostic, surgical or therapeutic devices. In the course of such procedures, it is common to advance introducers, dilators, and other tubular instruments over the probe and over one another in a prescribed sequence to enlarge the percutaneous pathway by spreading tissue apart. The probe is removed at a particular point in the procedure depending upon the selection of instruments that are used in the sequence of enlarging the percutaneous pathway.
In one approach, the percutaneous pathway that is finally created is defined by the lumen of a hollow tubular catheter or introducer or the like extending from the skin to the accessed site to enable passage of therapeutic or diagnostic or surgical devices therethrough to the accessed site. In another approach, the percutaneous pathway is defined by the outer guiding surface of a hollow or solid core stylet or guide wire extending from the skin to the accessed site to enable over-the-wire advancement of therapeutic or diagnostic or surgical devices to the percutaneous access site.
When the percutaneously accessed site is the site of interest, a diagnostic, surgical or therapeutic device is introduced through the expanded percutaneous pathway in the through-the-lumen or over-the wire manner to perform a procedure or deliver a therapy to the accessed site.
When a more remote site is the site of interest, the same or a further accessing instrument or tool, e.g. an elongated catheter or cannula or guide wire (or a combination of the same used in a predetermined sequence), is advanced through the percutaneous pathway and from the percutaneously accessed site through a remote access pathway to the remote site of interest. The access pathway may be a vascular pathway from an incision into a vein or artery at the percutaneously accessed site that is employed to introduce cardiac catheters and leads or vascular instruments for diagnostic, therapeutic or surgical procedures at remote sites in the heart or in the vascular system. Or the access pathway may be through or into a body organ or cavity or lumen or other structure to the remote site of interest.
Usually, the percutaneous pathway is relatively straight, but the access pathway twists and turns following the anatomy of the body. Typically, the accessing instrument that is left in place extending to the remote site comprises a flexible guide wire or guide catheter that can bend to follow the access pathway. The flexible guide wire or guide catheter then extends from an accessible proximal end left outside the patient""s body through the percutaneous pathway and the access pathway to a distal end advanced to the remote site. Then, a diagnostic or surgical or therapeutic instrument is introduced over-the-wire or through-the-lumen to enable a diagnostic or surgical procedure or to provide a therapy at the remote site.
Many therapeutic and/or diagnostic procedures have been developed that involve obtaining access to a desired percutaneous access site or remote site in the body as described above and the implantation of a temporary or permanent electrical stimulation lead, sensor bearing lead or drug delivery catheter that is coupled with a permanently implanted or external pulse generator and/or monitor or drug delivery device. In many procedures, it is desirable to insert a therapeutic or diagnostic lead or catheter having as small an outside diameter as is possible to locate a distal segment thereof at a desired site while minimally displacing body tissue. The electrical stimulation lead, sensor bearing lead or drug delivery catheter is implanted via such a percutaneous pathway and typically extends through an access pathway to locate electrical sensing and/or stimulation electrodes or sensors or drug delivery outlets at the remote site. In permanent implantation procedures, the proximal ends of such sensor and/or electrode bearing leads or catheters are coupled to implantable pulse generators and/or monitors or drug delivery devices that are implanted subcutaneously near the percutaneous pathway or at a distance from the percutaneous pathway. In the latter case, the lead or catheter is relatively long or is attached to a relatively long lead or catheter body that is implanted through a subcutaneous tunnel to the remote medical device.
For example, access to the epidural space of the spinal column and to introduce a stimulation lead into the epidural space is disclosed in commonly assigned U.S. Pat. No. 5,255,691. An epidural needle assembly is employed to reach a percutaneously accessed site in the epidural space, and a stylet stiffened stimulation lead is introduced through the needle lumen and advanced past the percutaneously accessed site through an access pathway in the epidural space to position the lead electrodes at a remote site still within the epidural space. The needle and stylet are withdrawn, and the lead connector elements are connected with an implantable neurostimulator that is implanted subcutaneously in the body.
As noted above, the initial step in forming a percutaneous pathway typically involves use of a probe, such as a stiff, sharp tip or blunt tip, straight needle, that is advanced by a clinician from the skin or skin incision to the percutaneously accessed site. In most cases, the probe is aimed in a carefully determined direction from the skin to the site so that the distal tip of the needle reaches the site of interest with the needle axially aligned to body feature that must be accessed. For example, percutaneous pathways are formed to allow miniaturized neurostimulation leads to be advanced into the spinal column as disclosed, for example, in the above-referenced ""691 patent, or through a foramen of the sacrum (as disclosed, for example, in commonly assigned U.S. Pat. Nos. 5,957,965, 6,104,960 and 6,055,456) in carefully determined and particularly sensitive directions.
The direction of advancement of the needle or other probe in three-dimensional space is determined in advance by use of radiographic imaging or palpation of tissue or stealth station technology. The probe is then carefully held and advanced from the skin so that it is axially aligned with the predetermined direction. This procedure is most easily accomplished using a probe that is no longer than necessary to extend from the skin to the percutaneously accessed site. It is easier to accurately aim and advance a short probe than a long probe that extends away from the skin. The probe is necessarily small in diameter and stiff, and such a probe tends to flex and bend in direct relation to its length. Thus, a long probe can bend as it is advanced and depart from the intended direction. Moreover, the probe becomes more difficult to aim and hold to a desired direction as its length increases, because slight deviations from the intended direction are magnified through the length of the probe.
Therefore, relatively short probes are employed having a shorter exposed length extending from the skin than the length of a lead or catheter or instrument that is to be advanced through the percutaneous pathway. Typically, the probe length is shorter than the overall length of the lead or catheter which usually includes a proximal segment that is to be extended to an external or implanted device located or implanted at a distance from the percutaneous pathway. Thus, it is not possible to grasp the proximal end of the probe if an attempt is made to advance any such lead or catheter or instrument over the probe to maintain the carefully determined direction of insertion of the probe.
We have found that it would be desirable to be able to employ the probe itself to guide longer dilators or surgical instruments or leads or catheters or the like in an over-the-wire manner to a remote site or just to the percutaneous access site to minimize the number of instruments used and steps in the procedure.
Accordingly, the present invention recognizes and provides a solution to the problems associated with defining a percutaneous pathway for over-the-wire advancement of a therapeutic or diagnostic instrument or a pathway expanding instrument.
In accordance with a preferred embodiment of the invention, a combined percutaneous medical probe and guide wire is employed to form a percutaneous pathway to a percutaneously accessed site and enables over-the-wire advancement of an elongated medical device to the percutaneously accessed site and into an access pathway. The combined medical probe eliminates the need to introduce a separate guide wire to the percutaneously accessed site.
The combined percutaneous medical probe and guidewire comprises a stiff tissue penetrating probe having a first length adapted to provide the percutaneous pathway to the percutaneously accessed site of interest. The tissue penetrating probe is coupled with a flexible guide wire body that remains entirely or substantially outside the body having a second length sufficiently long to support the full length of the elongated medical device to enable its over-the-wire advancement. The tissue penetrating probe is adapted to be manually grasped, aligned axially in a predetermined direction, and advanced from the skin to the percutaneously accessed site while the flexible guide wire droops away from the attachment with the proximal end of the probe. Thus, the relatively short probe is more readily and accurately aligned to the predetermined direction to facilitate accurate advancement. Then, a further instrument, e.g. a dilator having a through-lumen, can be advanced over the flexible guide wire body and distally over the probe to dilate the tissue surrounding it if necessary. An elongated medical device having a through-lumen comprising one of a lead or a catheter or a surgical instrument can be inserted over the combined flexible guide wire body and the probe to locate a distal end thereof at the percutaneously accessed site or through the percutaneously accessed site to a remote site in the body.
The percutaneously accessed site is typically within a vessel or organ lumen or within the brain or within a body cavity that is reached by the distal end of the probe that is passed through the skin and subcutaneous tissue. The combined medical probe can be employed as a test stimulation or electrical sensing lead to apply electrical stimulation to responsive tissue, e.g., muscle or nerve fibers or brain cells, or to receive electrical signals from tissue at the percutaneously accessed site. The probe is preferably formed of conductive metal and electrically insulated along its length except for a stimulation or sense electrode area at or adjoining the probe distal tip. The flexible guide wire is preferably formed of an electrical conductor that is electrically insulated along its length except for a proximal electrode connector element.
Preferably, the probe is formed of a needle with a closed distal tip to prevent coring of tissue. The flexible guide wire body is preferably formed of a coiled wire within an insulating sheath having a guide wire body diameter about equal with the diameter of the needle. An inextensible core wire is fixed to and extends from the exposed proximal end of the coiled wire through the coiled wire lumen and the needle lumen to the beveled needle distal tip and thereby inhibits stretching of the guide wire body and coring of tissue by the needles distal tip. Alternatively, the core wire can be affixed more proximally within the needle lumen or otherwise fixed to the needle proximal end, and the needle lumen can be filled with a further wire or filler material to provide an equivalent structure. The continuous core wire provides a continuous electrical conductor that is relatively noise free when the combined medical probe and guide wire is used as a stimulation or electrical sensing lead.
One preferred use of the combined percutaneous medical probe and guide wire is to form a percutaneous pathway to a sacral nerve that can be accessed in a posterior approach through a foramen of the patient""s sacrum where the sacral nerve extends anteriorly and inferiorly so as to place an implantable neurostimulation lead electrode in operative relation with the sacral nerve. In this procedure, it is important to accurately insert the probe tip into the foramen at a prescribed angle to access the sacral nerve without damaging it. The sacral nerve response to applied electrical test stimulation can be assessed at differing depths of insertion of the exposed distal tip electrode to map the optimal location of the lead electrode.
If necessary, dilation of tissue around the probe can be undertaken. A dilator can be advanced over the guide wire body until the guide wire proximal end is exposed from the dilator lumen at the lead body proximal end. The guide wire body can be straightened to enable advancement of the dilator over the probe and withdrawal of the dilator.
A neurostimulation lead can be advanced over the guide wire body until the guide wire proximal end is exposed from the lead body lumen at the lead body proximal end.
The guide wire body can be straightened to enable advancement of the lead over the probe until the neurostimulation lead electrode(s) is optimally advanced into operative relation to the sacral nerve. The sacral nerve response to applied electrical test stimulation can also be tested using the neurostimulation lead as the lead electrode is advanced. The combined probe and guide wire can be retracted from the lead body lumen when the testing is completed and the distal stimulation electrode(s) is optimally placed. The implantation procedure of the present invention employing the combined percutaneous medical probe and guide wire to form a percutaneous pathway for implanting a neurostimulation lead allows more rapid placement of the stimulation electrodes near the sacral nerves.
A similar procedure can be undertaken using the to implant leads and catheters or to guide tissue expanding introducers or dilators to other percutaneously accessed sites using the combined percutaneous medical probe and guide wire is to form a percutaneous. pathway. For example, the combined percutaneous medical probe and guide wire can be used to form a percutaneous pathway into the epidural space of the spinal column, into or adjacent to the stomach wall for the treatment of stomach disorders such as gastroparesis, into the large intestine for treatment of a paralyzed bowel condition or delayed bowel. Moreover, the combined percutaneous medical probe and guide wire can be used to form a percutaneous pathway through chest wall into the pericardial sac to provide a pathway to advance a cardiac pacing lead for treatment of bradycardia or a lead bearing a physiologic sensor to the pericardium. The lead may have a fixation mechanism for affixing pace/sense electrodes against the pericardium or into the myocardium.
This summary of the invention has been presented here simply to point out some of the ways that the invention overcomes difficulties presented in the prior art and to distinguish the invention from the prior art and is not intended to operate in any manner as a limitation on the interpretation of claims that are presented initially in the patent application and that are ultimately granted.